So, after a while of settling into my new home I got down to putting my first SCP idea onto paper, and now I would love for someone to assist with proof reading, since I do not trust my own English Grammar.

Some purely technical feedback:
"10 m" > "10m"
"air-tight" > "airtight"
"Infected Personal" > "Infected personnel"
"personal" > "personnel"
"closed circuit" > "sealed"?
"SCP-XXXX is an undetectable being unless infected by surrounding pathogen (SCP-XXXX-1)." > "SCP-XXXX is an entity undetectable unless infected by the pathogen designated SCP-XXXX-1"?
"rotten off" > "decomposed"?
"SCP-XXXX’s skin has undergone heavy stages of decomposition, and in many cases is infested with maggots." > "SCP-XXXX's skin appears to be in an advanced stage of decomposition and infested with maggots"
"Pathogen however is only infectious within a 10m radius." > "The pathogen is infectious within a 10m radius of SCP-XXXX." (presume this is the intent).
"SCP-XXXX-1 travels" - do you mean "SCP-XXXX travels"?
"subjects (Referred" > "subjects (referred"
"over-whelming" > "overwhelming"
"Incidents reported" > "observed injuries include"?
"All interviews after initial infection have been inconclusive in further information." > "Interviews with subjects after initial infection have been largely inconclusive in terms of obtaining further information." - they've provided some information about SCP-XXXX, such as its appearance
"hat monster?" - this seems like a typo
"thrachea" > "trachea"
"Addendum: After incident [DATA EXPUNGED], personal reporting ANY signs of infection are to be immediately terminated and disposed of." >
"Addendum XXXX-01

After Incident XXXX-1, personnel reporting any signs of infection are to be immediately terminated and disposed of."

This really seems like it should be elaborated upon - my general rule is that the contents of a 'DATA EXPUNGED' should always be hinted at elsewhere. I also imagine you're going to get criticism on tone here; nothing else in the article indicates that infected individuals are such an extreme risk to warrant executing, for example, researchers who have been accidentally infected.

Thanks a lot, looking at the terrible grammar and obvious typos I had, I could only shake my head in sorrow at how bad that was.
I made the appropriate changes, however I had to point out that 'Closed Circuit' is a term for a respiratory type, using stored Oxygen. (Like SCBA/SCUBA Gear.)
Also I have to get the image for it finished, that will hopefully clear up its appearance.

One last thing— What do you mean by this edit: "subjects (Referred" > "subjects (referred" ?

Thanks - just a capitalisation issue: generally you don't start asides within brackets with a capital letter. A word of caution if you plan to introduce an image - how has it been taken? You establish that the skip is undetectable except to those who have been infected, so presumably taking a photo of it is out (as otherwise non-infectees could perceive it by, for example, keeping it under CCTV surveillance).

Hopefully I or someone of better artistic talents, could do sketches. I am aiming at having a few pictures, ranging from hastily sketched from panicked subjects, to artists renditions from all the sketches.

Also, thanks for the edits, especially without being snobbish about it.